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Ar/Co2 for SS MiG ?

11-12-2008, 10:38 PM

I need to tack the slip joints on a 4" stainless exhaust system and was wondering if it's ok to use Ar/Co2 since this is about all I'm going to be doing with stainless. I want the welds to be permanent and strong enough to hold the joints together w/o clamps, but really don't want to buy a bottle of gas just for 6 or 8 tack welds.

Comment

Comment

If the stainless welding is for anything else please be careful. The stainless code is VERY specific about how much CO2 can be used. The issue is chromium carbides that will make the corrosion effect more rapid and lead to premature failure. More than 3% CO2 is not allowed according to table 3.5 of the prequalified clause in AWS D1.6 2007.

That being said I realize you are not welding stainless structural steel, but the reasoning behind the limitation is sound. Clause 4 does allow for your own qualification testing.

I would be careful as well if there is going to be dramatic heat fluxuations in the part.

There, I have spoken my peace. You are free to do as you please, just be ready for what will come after it.